In recent years, the structure of a design object such as an apparatus is often numerically analyzed by computer simulations in its design stage. The technology of numerically simulating physical phenomena using a computer is referred to as CAE (Computer Aided Engineering). In such a numerical analysis simulation, contact definitions may be applied in advance to the components of an apparatus to be analyzed. More specifically, the numerical analysis software that performs the numerical analysis simulation makes a contact determination as to whether or not contact occurs between components, on the basis of the contact definition therebetween each time the components are deformed.
When contact definitions are not applied to components, problems may occur after execution of the numerical analysis simulation. One problem that can occur when contact definitions are not applied will be described with reference to FIG. 19. FIG. 19 is a diagram illustrating the problem when contact definitions are not applied. As illustrated in FIG. 19, an external force is applied to a component in a state in which all components are undeformed to bring them in a deformed state. Then components to which a contact definition has been applied come in contact with each other. However, in components to which no contact definition has been applied, a phenomenon called penetration in which one component is embedded in another component can occur, resulting in a problem that it is difficult for the numerical analysis to be performed appropriately.
In one means for contact definitions that can prevent the occurrence of the above problem, a user selects, using a modeler that assists the production of a 3D geometrical model, the geometrical surfaces of components represented by the 3D model to apply contact definitions to these components. In another means for contact definitions, a modeler automatically detects the geometrical surfaces of components spaced apart by a user specified distance or less to apply contact definitions to these components.
In one technique used when the geometrical surfaces of components are divided into a mesh, the contact regions of two components are defined as follows. The distances between each divided region of one component and divided regions of the other component that have normal vectors substantially opposite to the normal vector of the each divided region are determined, and the divided regions of these components that are closest to each other are used as the contact regions.    Patent Document 1: Japanese Laid-open Patent Publication No. 2009-059028    Patent Document 2: Japanese Laid-open Patent Publication No. 06-266807    Patent Document 3: Japanese Laid-open Patent Publication No. 2006-048583
However, with the conventional techniques of contact definitions between components, the contact definitions are applied to the geometrical surfaces of the components. Therefore, in a numerical analysis simulation performed after the contact definitions are applied, unnecessary contact determinations may be made, and this results in a problem that the numerical analysis time increases.
The conventional contact definitions between components will be described with reference to FIGS. 20 and 21. FIG. 20 is a diagram illustrating specific examples of contact areas between components, and FIG. 21 is a diagram illustrating the conventional contact definitions. In components A, B, C and D illustrated in FIG. 20, when a load is applied to the component A in the direction toward the component B, a surface of the component A that is on the side toward the component C comes into contact with a surface of the component C that is on the side toward the component A, and a surface of the component A that is on the side toward the component D comes into contact with a surface of the component D that is on the side of the component A. More specifically, in the surface of the component A, a surface A-C and a surface A-D are surfaces E that have the possibility of coming into contact with other components, and the other region is a region F that has no possibility of coming into contact with other components.
However, as illustrated in FIG. 21, in the conventional contact definitions, to define contact between the components A and C, a contact definition d1 is applied to a surface m1 of the component A that is on the side toward the component C and a surface m2 of the component C that is on the side toward the component A. More specifically, on the surface of the component A that is on the side toward the component C, the contact definition is applied to a region including a region F that has no possibility of coming into contact with the component C. Therefore, in a numerical analysis simulation performed after the contact definition is applied, the numerical analysis software makes unnecessary contact determinations, and this results in an increase in the numerical analysis time. This also occurs for a contact definition d2 applied between the surface m1 of the component A that is on the side toward the component B and a surface m4 of the component B that is on the side toward the component A and for a contact definition d3 applied between a surface m3 of the component D that is on the side toward the component B and the surface m4 of the component B that is on the side toward the component D.
In contact definitions applied between components using a modeler, the user makes contact determinations, and therefore omission of contact definitions can occur. When contact definitions between some components are omitted, the omitted contact definitions is applied separately, and then a numerical analysis simulation is performed. This results in a problem that the numerical analysis time increases.
When contact definitions are applied using the normal vectors of surface regions of components, the geometrical surface of each component must be divided into a mesh of surface regions. Therefore, contact definitions cannot be applied directly to the geometrical surfaces of the components.